DE102011078424A1 - Methods and apparatus for creating addresses for subscribers in a network - Google Patents

Abstract

The invention relates to methods and apparatus for creating addresses for subscribers in a network such that hash collisions due to the assignment of the addresses are avoided.

Description

The invention relates to methods and apparatus for creating addresses for subscribers in a network.

In addition to traditional communication networks, more and more autonomous subscribers, such as network nodes or terminals, exchange data with one another. Thus, in addition to large networks with several hundred participants, a variety of small networks with, for example, up to 100 participants.

An addressing of these subscribers happens, for example, by means of MAC addresses (MAC - Media Access Control) with a 2 ^ 48 address space (^ means to power, so 2 ^ 48 is equivalent to 2 high 48), IPv4 addresses with a 2 ^ 32 Address space and IPv6 addresses with a 2 ^ 128 address space (IP - Internet Protocol, v4 / v6 - version 4/6).

The respective address of the subscribers is stored at certain points in the network, such as in a switch that controls a distribution of data packets for subpaths according to OSI layer 2 (OSI Open Systems Interconnection).

It is disadvantageous that, especially in large networks with a large number of subscribers, storing the addresses means a considerable amount of memory. In addition, a search for an address with many places in a forwarding table (= forwarding table) is expensive.

Therefore, in a routing table, abbreviated addresses, which will be referred to as address values in the following, may be used instead of "real" addresses. For this purpose, the address is, for example, converted by means of a hash function [1] into the address value, that is, for example, from the address with 48 bits into an address value with 12 bits. It is obvious here that a reduction of the address length achieves the memory requirement as well as an acceleration in the search for an address value in the routing table.

However, the shortening of the address also requires that different addresses be encoded by the hash algorithm to an identical address value. This is called a hash collision.

One approach to this problem is to provide a memory area in the form of a list in the case of hash collisions, in which addresses with the same hash value are entered. This does not solve the problem satisfactorily because a number of list entries and thus a permissible number of addresses with the same hash value are still limited. When searching for an address by means of the address value, this results in a considerable amount of time.

Another approach is described in [2]. An implementation of a hash function optimized for a specific address distribution in LAN local area network switches is presented. However, this approach is associated with a considerable implementation effort and therefore usually leaves for commercial applications.

Therefore, the object is to provide methods and devices that avoid a hash collision and allow easy implementation.

This object is solved by the independent claims. Further developments of the invention can be found in the dependent claims.

• i) Bereitstellen des zweiten Adresswerts des zweiten Teilnehmers durch Anwenden einer Hash-Funktion auf Basis der zweiten Adresse;
• ii) Erstellen der ersten Adresse aus einer Menge an möglichen Adressen derart, dass sowohl die erste Adresse unterschiedlich zu der zweiten Adresse ist als auch der erste Adresswert des ersten Teilnehmers, der durch Anwenden der Hash-Funktion auf Basis der ersten Adresse generiert wird, unterschiedlich zu dem zweiten Adresswert ist.

The invention relates to a method for establishing a first address of a first subscriber in a network with the first subscriber and at least one second subscriber, wherein the second subscriber has a second address, and a length of the addresses is longer than a length associated with the addresses Address values, with the following steps:

• i) providing the second address value of the second subscriber by applying a hash function based on the second address;
• ii) creating the first address from a set of possible addresses such that both the first address is different than the second address and the first address value of the first user generated by applying the hash function based on the first address to the second address value.

This method is advantageous because a complex error handling in the case of hash collisions can be avoided. In addition, a storage space for storing z. For example, it reduces routing information for address values in routers or switches because there are no exceptional cases for hash collisions. In addition, a time to process lists based on address values is reduced because no hash collision routines need to be edited.

The address means an address of a subscriber in a network, e.g. B. sender and / or recipient address. A length of the address, z. B. 48 bit, is longer than a length of the address value assigned to the address, z. Eg 12bit. Thus, the address generally has more bits than the address value that can be assigned by means of the hash function. Address can be understood as an IP address according to IPv4 or IPv6 (IP Internet Protocol, v4 / v6 version 4/6) or even a MAC address (MAC Media Access Control). Further details can be found in the introduction.

The hash function is any algorithm that transforms the address into an address value that is shorter in length than the address. A hash function can be a classical hash algorithm, such as known from a document [1].

In addition, the invention can be implemented by a method for creating a first address of a first subscriber for a network, which has at least two further subscribers with associated further addresses, and a length of the addresses is longer than a length of address values belonging to the addresses following the steps below:
Determining two further address values using a hash function based on the two further addresses; Create, if the two further address values are identical, the first address for the first further subscriber as the first subscriber, taking into account a second address, which is the further address of the second further subscriber, from a set of possible addresses such that both the first address different from the second address, as well as the first address value of the first subscriber generated by applying the hash function based on the first address is different from a second address value which is the further address value of the second further subscriber;
Assigning the first address to the first further subscriber if the two further address values are identical.

This variant of the method makes it possible in an existing system to change addresses which cause a hash collision in pairs in such a way that the hash collision can be avoided. The resulting advantages are analogous to the previously described method.

• a) Wählen einer der möglichen Adressen als erste Adresse;
• b) Generieren des ersten Adresswerts;
• c) Vergleichen des ersten Adresswerts mit dem zweiten Adresswert;
• d) Wiederholen der Schritte a) bis d) falls der erste Adresswert identisch zu dem zweiten Adresswert ist.

In a first extension of the procedure, the creation of the first address is performed as follows:

• a) selecting one of the possible addresses as the first address;
• b) generating the first address value;
• c) comparing the first address value with the second address value;
• d) repeating steps a) to d) if the first address value is identical to the second address value.

This allows a simple and reliable implementation of the method step "creating the first address".

As an alternative to the first extension, creating the first address in a second extension can be done as follows:
Creating the set of possible addresses such that all address values formed by applying the hash function based on the possible addresses are each pairwise different, and the second address is not part of the set; Selection of one of the possible addresses of the set as the first address.

This allows a simple and reliable implementation of the method step "creating the first address". In addition, this second enhancement usually achieves a faster selection than the first enhancement, since a "try out" of candidates for the first address, as in the first extension, is eliminated.

The second extension can be supplemented in an advantageous manner by deleting the first address from the set after selection of one of the possible addresses, whereby the selection is further accelerated, since only unallocated addresses are taken into account in the selection.

The invention further relates to an apparatus for establishing a first address of a first party in a network with the first party and at least one second party, the second party having a second address, and a length of the addresses being longer than a length of the addresses associated address values, by the following means:
First means for providing the second address value of the second party by applying a hash function based on the second address;
Second means for selecting the first address from a set of possible addresses such that both the first address is different from the second address and the first address value of the first user generated by applying the hash function based on the first address; is different from the second address value.

The advantages of the device are analogous to those of the corresponding method steps.

The invention also relates to a device for generating a first address of a first subscriber for a network, which has at least two further subscribers with associated further addresses, and the addresses are longer than address values associated with the addresses, by the following means:
First means for determining the two further address values using a hash function based on the two further addresses;
Second means for creating, if the two further address values are identical, the first address for the first further subscriber as the first subscriber, taking into account a second address which is the further address of the second further subscriber, from a set of possible addresses such that both the first address different from the second address is as well as the first address value of the first user generated by applying the hash function based on the first address different from a second address value being the further address value of the second another user ;
Third means for assigning the first address to the first further subscriber if the two further address values are identical.

The advantages of this extension of the device are analogous to those of the corresponding method steps.

• a) Wählen einer der möglichen Adressen als erste Adresse;
• b) Generieren des ersten Adresswerts;
• c) Vergleichen des ersten Adresswerts mit dem zweiten Adresswert;
• d) Wiederholen der Schritte a) bis d) falls der erste Adresswert identisch zu dem zweiten Adresswert ist.

In a first extension of one of the devices, the second means for creating the first address is set up in such a way that the following steps are feasible:

• a) selecting one of the possible addresses as the first address;
• b) generating the first address value;
• c) comparing the first address value with the second address value;
• d) repeating steps a) to d) if the first address value is identical to the second address value.

The advantages of this extension of the device are analogous to those of the corresponding method steps.

In a second extension of one of the devices, the second means for creating the first address is arranged such that the following steps are feasible: generating the set of possible addresses in such a way that all address values formed by applying the hash function on the basis of the possible addresses, in pairs are different, and the second address is not part of the set; Selection of one of the possible addresses of the set as the first address.

The advantages of this extension of the device are analogous to those of the corresponding method steps.

Advantageously, the second means is further adapted to delete the first address from the set after selecting one of the further addresses. This further speeds up the selection, as only addresses that have not yet been allocated are taken into account in the selection.

Preferably, the method can be used in a switch of a network, wherein the network is in particular an administered network. As a result, in the administered network (= Locally Administered Network according to IEEE 802 ) avoid switch hash collisions, allowing a more efficient implementation of the switch.

The invention and its developments are explained in more detail with reference to figures. Show it

1 A network with a first and second subscriber and a device in the form of an assignment unit according to a first embodiment

2 How a hash function works

3 A network with a first further and second further participants according to a further embodiment

4 Flowchart of a method and structure of a device

Elements with the same function and mode of operation are provided in the figures with the same reference numerals.

1 shows a network NET with two participants T1, T2 and a device DEV, which is also referred to as an assignment unit. The allocation unit and subscribers can send messages to exchange data via paths P1, P2, P3. These paths are realized, for example, by means of copper wire lines, whereby data can be exchanged by means of MAC (MAC-Media Access Control) addressing. The assignment unit DEV has the task of receiving a request message from a subscriber to this configuration data, such as to send its MAC address. Such MAC addresses are referred to as addresses in this example. The network NET is, for example, a network with "locally administered addresses" (= locally administered addresses) according to a Standard IEEE 802 (IEEE Institute of Electrical and Electronics Engineers).

The second subscriber T2 has a second address L2 with 01.44.8A.BC.AA.64. In the following explanations, all addresses are displayed in hexadecimal notation. When the first subscriber T1 is switched on, the latter sends a request message to the allocation unit DEV. The allocation unit selects from a set ML of possible addresses a first address L1 for the first subscriber. The procedure is as follows:

First step S1:

A second address value K2 of the second subscriber T2 is formed by applying a hash function HASH on the basis of the second address L2. The hash function, see for example document [1], maps the address with 48 bits into an address value with 8 bits. In this example, the hash function discards the first 40 bits of the address and generates a remainder resulting from dividing the last 8 bits of the address by a value of 7. Thus, the second address value K2 is calculated to be 2.

Second step S2:

The assignment unit extracts the first address L1 from the set ML. The first address L1 is EF.01.B2.F9.79.37. The associated first address value K1 results in 6. Thus, both the first and second address and the first and second address value are different, so that a valid first address was determined.

This first address transmits the assignment unit DEV in the form of a reply message to the first subscriber. Thus, only addresses are available in the network whose address value can be uniquely assigned to an address. This avoids a hash collision. The term hash collision is known from the prior art.

In a variant of the above example, the allocation unit DEV first selects the first address L1 equal to A1.B2.C3.D4.E5.41 for the first subscriber. The associated first address value is 2. Since the first and second address value K1 = K2 is identical, the above selection of the first address is discarded and searched for a first address in the set of possible addresses until a first address is found, the associated first address value is different from the second address value.

Alternatively, the allocation unit may set the amount of possible addresses in advance. In this case, only addresses are added to the set ML which lead to address values which are not generated by addresses already contained in the set ML. For the above hash function a maximum of 7 different address values 0 to 6 can be generated so that a maximum of 7 addresses can be included in the set ML, as shown in the following list: address address value A0.7F.88.00.FF.07 0 CC.6A.FF.FF.90.78 1 01.44.8A.BC.AA.64 2 A1.B2.C3.D4.E5.42 3 00.00.10.DD.00.C8 4 00.00.FF.00.66.9F 5 EF.01.B2.F9.79.37 6

To simplify the management of this list, already assigned addresses from the set ML can be deleted. Therefore, after assigning the first and second addresses, the following new list results: address address value A0.7F.88.00.FF.07 0 CC.6A.FF.FF.90.78 1 A1.B2.C3.D4.E5.42 3 00.00.10.DD.00.C8 4 00.00.FF.00.66.9F 5

In 1 In addition to the participants already explained and the allocation unit, a switch R can still be seen on the edge of the network. A switch mediates data packets on an OSI layer 2 (OSI-Open Systems Interconnection), eg. B. in the so-called MAC camp (= MAC layer). The switch determines on which path or partial path of three possible paths P1, P2, P3 a packet of the first subscriber T1 is forwarded. The forwarding decision made by the switch relates to 1 the path from the set of paths. In another example, the forwarding decision may involve only a partial path, from the switch to a next-in-place switch or hop. To perform the forwarding decision, the switch takes the destination address as the address from the received packet and reduces it to its associated address value. Internally, the switch has a Forwading Table, in which an assignment between the address value and the path or subpath is stored, which, for example, looks like this: address value Part Path Path / 2 P3 6 P1

Thus, the switch is able to use the address value to determine the further route or partial path of the packet or message.

This embodiment shows the invention based on fewer participants. With several hundred participants with long addresses, z. B. 128 bit, the invention achieves a significant memory space reduction in the above forwarding list, which can be efficiently traversed by the address value based on the address sought.

3 shows an existing network NET, in which there are two further participants TW1, TW2 with already assigned further addresses LW1, LW2 with LW1 = A0.7F.88.00.FF.07 and LW2 = AB.4F.4E.00.00.0E. The determination of the two further address values KW1, KW2 belonging to the two further addresses LW1, LW2 shows that both address values KW1 = KW2 = 0. Thus, the switch R can not differentiate the other participants based on their associated address values. Therefore, the allocation unit assigns a new address to one of the other two subscribers, such as, for example, the first further address LW1 = A1.B2.C3.D4.E5.42. In this case, either the original additional address can be replaced by the new address or the other subscriber receives the new address as an additional address, which he rewrites upon receipt of a packet in the original further address or when sending a packet with the original further address in the new address changes. Instead of the other participant can also another Unit (not shown in the figure) the implementation of the address from the original address to the new address and vice versa.

The invention and its developments can be realized by means of a device DEV for creating a first address L1 of a first subscriber T1 in a network NET with the first subscriber T1 and at least one second subscriber T2, wherein the second subscriber T2 has a second address L2, and a length of the addresses L1, L2 is longer than a length of address values K1, K2 associated with the addresses L1, L2, by the following means M1, M2:
First means M1 for providing the second address value K2 of the second subscriber T2 by applying a hash function HASH on the basis of the second address L2;
Second means M2 for selecting the first address L1 from a set ML of possible addresses such that both the first address L1 is different from the second address L2 and the first address value K1 of the first subscriber T1, which is obtained by applying the hash function HASH is generated on the basis of the first address L1 is different from the second address value K2.

Furthermore, the device DEV can be designed to create a first address L1 of a first subscriber T1 for a network NET, which has at least two further subscribers TW1, TW2 with associated further addresses LW1, LW2, and a length of the addresses L1, L2, LW1, LW2 is longer than a length of address values K1, K2, KW1, KW2 belonging to the addresses L1, L2, LW1, LW2 by the following means M1, M2, M3:
First means M1 for determining the two further address values KW1, KW2 using a hash function HASH based on the two further addresses LW1, LW2;
Second means M2 for generating, if the two further address values KW1, KW2 are identical, the first address L1 for the first further subscriber TW1 as the first subscriber T1, taking into account a second address L2, which is the further address LW2 of the second further subscriber TW2, from a set ML of possible addresses such that both the first address L1 is different from the second address L2 and the first address value K1 of the first user T1 generated by applying the hash function HASH on the basis of the first address L1, different from a second address value K2, which is the further address value KW2 of the second further subscriber TW2;
Third means M3 for assigning the first address L1 to the first further subscriber TW1 if the two further address values KW1, KW2 are identical.

4 shows the sequence of the method with the steps S1 and S2. Furthermore, the 4 also to take the device DEV. This device comprises a first means M1 for carrying out the first step S1 and a second means M2 for carrying out the second step S2, wherein the second means M2 can also be used to carry out extensions of the method of the invention. In addition, the device may have a third means M3, which is designed to associate the first address. The means M1, M2, M3 can be implemented in hardware, software or in a combination of hardware and software. For example, a processor executes the steps S1 to S2 stored as program code in a memory attached to the processor and, if necessary, further steps of extensions of the method. Furthermore, the processor has an input and output interface with which the request message can be read in and the first address can be provided to the first user in the form of a response message. In addition, intermediate results of the individual processing steps, such as, for example, the address values K1, 0K2 or the quantity ML can additionally be stored in the memory. Furthermore, the means M1, M2 and M3 can also be realized by a fixed wiring of electronic components with a memory module.

The invention and its developments have been explained with reference to several examples. However, the invention is not limited only to the examples. In addition, the embodiments can also be combined.

literature

• [1] Hash Function, Wikipedia article, found on June 21, 2011, http://en.wikipedia.org/wiki/Hash_function

[2] Huntley, C. et al. "Effect of Hash Collisions on the Performance of LAN Switching Devices and Networks," IEEE Conference on Local Computer Networks, ISBN: 1-4244-0418-5, Nov. 14-16, 2006, pages 280-284

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• IEEE 802 [0032]
• Standard IEEE 802 [0039]
• Huntley, C. et al. "Effect of Hash Collisions on the Performance of LAN Switching Devices and Networks," IEEE Conference on Local Computer Networks, ISBN: 1-4244-0418-5, Nov. 14-16, 2006, pp. 280-284 [0055]

Claims (11)

Method for creating a first address of a first subscriber (T1) in a network (NET) with the first subscriber (T1) and at least one second subscriber (T2), the second subscriber (T2) having a second address (L2), and a length of the addresses (L1, L2) is longer than a length of address values (K1, K2) associated with the addresses (L1, L2), comprising the following steps: i) providing the second address value (K2) of the second subscriber (T2) by applying a hash function (HASH) based on the second address (L2); ii) constructing the first address from a set (ML) of possible addresses such that both the first address is different from the second address (L2) and the first address value (K1) of the first user (T1) obtained by applying the Hash Function (HASH) is generated based on the first address, which is different from the second address value (K2). Method for creating a first address of a first subscriber (T1) for a network (NET), which has at least two further subscribers (TW1, TW2) with associated further addresses (LW1, LW2), and a length of the addresses (L1, L2, LW1, LW2) is longer than a length of address values belonging to the addresses (L1, L2, LW1, LW2) (K1, K2, KW1, KW2) in which the following steps are performed: Determining the two further address values (KW1, KW2) using a hash function (HASH) based on the two further addresses (LW1, LW2); Create, if the two further address values (KW1, KW2) are identical, the first address for the first further subscriber (TW1) as the first subscriber (T1) taking into account a second address (L2) containing the further address (LW2) of the second another subscriber (TW2) is made up of a set (ML) of possible addresses in such a way that both the first address is different from the second address (L2) and the first address value (K1) of the first user (T1) the hash function (HASH) is generated on the basis of the first address, different from a second address value (K2), which is the further address value (KW2) of the second further subscriber (TW2); Assigning the first address (L1) to the first further subscriber (TW1) if the two further address values (KW1, KW2) are identical. Method according to claim 1 or 2, where the first address is created as follows: a) selecting one of the possible addresses as the first address; b) generating the first address value (K1); c) comparing the first address value (K1) with the second address value (K2); d) repeating steps a) to d) if the first address value (K1) is identical to the second address value (K2). Method according to claim 1 or 2, where the first address is created as follows: Creating the set (ML) of possible addresses such that all address values formed by applying the hash function based on the possible addresses are each pairwise different, and the second address (L2) is not part of the set (ML); Selection of one of the possible addresses of the set (ML) as the first address. The method of claim 4, wherein The following steps are performed after selecting the first address: Delete the first address from the set (ML). Device (DEV) for creating a first address of a first subscriber (T1) in a network (NET) with the first subscriber (T1) and at least one second subscriber (T2), the second subscriber (T2) having a second address (L2) and a length of the addresses (L1, L2) is longer than a length of address values (K1, K2) associated with the addresses (L1, L2) by the following means (M1, M2): First means (M1) for providing the second address value (K2) of the second party (T2) by applying a hash function (HASH) based on the second address (L2); Second means (M2) for selecting the first address from a set (ML) of possible addresses such that both the first address is different from the second address (L2) and the first address value (K1) of the first user (T1), generated by applying the hash function (HASH) based on the first address is different from the second address value (K2). Device (DEV) for creating a first address of a first subscriber (T1) for a network (NET), which has at least two further subscribers (TW1, TW2) with associated further addresses (LW1, LW2), and a length of the addresses (L1 , L2, LW1, LW2) is longer than a length of addresses belonging to the addresses (L1, L2, LW1, LW2) (K1, K2, KW1, KW2) by the following means (M1, M2, M3): First means (M1) for determining the two further address values (KW1, KW2) using a hash function (HASH) on the basis of the two further addresses (LW1, LW2); Second means (M2) for creating, if the two further address values (KW1, KW2) are identical, the first address for the first further subscriber (TW1) as the first subscriber (T1) taking into account a second address (L2), the further Address (LW2) of the second further subscriber (TW2) is, of a set (ML) of possible addresses, such that both the first address is different from the second address (L2) and the first address value (K1) of the first subscriber ( T1) generated by applying the hash function (HASH) based on the first address, different from a second address value (K2) which is the further address value (KW2) of the second further user (TW2); Third means (M3) for assigning the first address (L1) to the first further subscriber (TW1) if the two further address values (KW1, KW2) are identical. Device (DEV) according to claim 6 or 7, wherein the second means (M2) for establishing the first address is arranged such that the following steps are feasible: a) selecting one of the possible addresses as the first address; b) generating the first address value (K1); c) comparing the first address value (K1) with the second address value (K2); d) repeating steps a) to d) if the first address value (K1) is identical to the second address value (K2). Device (DEV) according to claim 6 or 7, wherein the second means (M2) for establishing the first address is arranged such that the following steps are feasible: Creating the set (ML) of possible addresses such that all address values formed by applying the hash function based on the possible addresses are each pairwise different, and the second address (L2) is not part of the set (ML); Selection of one of the possible addresses of the set (ML) as the first address. Device (DEV) according to claim 9, wherein the second means (M2) is further adapted to cancel the first address (L1) from the set (ML) after selecting one of the possible addresses. Use of the method according to one of claims 1 to 5 in a switch of a network (NET), wherein the network (NET) is in particular an administered network.

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